FI4060206T3 - Device for mechanical locking of a linear movement between two structures - Google Patents

Description

DEVICE FOR MECHANICAL LOCKING OF A LINEAR MOVEMENT

BETWEEN TWO STRUCTURES

FIELD OF THE INVENTION

The invention relates to a device capable of allowing the relative movement of two structures with respect to one another under normal conditions of use or situation and, relatedly, of blocking this movement when said so-called normal conditions are not met anymore. This device is intended in particular to protect all or part of the constituent — elements of said structures.

In particular, it finds application: " within oscillating mechanisms of the balance type, to allow the movement of said balance to be blocked in the event of a rapid imbalance, such as in the field of hoisting winches for example; = within seismic stops; = within stops for air/hydraulic valves/doors, in order to block this system in the event of sudden stresses inherent to the windstorms, explosions, etc.; = within the protection of the mechanisms of doors, traps or hatches, in order to protect the opening mechanisms in the event of an explosion or exceptional stress; " within the stabilisation of equipment subject to strong accelerations in the field of aeronautics, maritime and land vehicles; = within pipework supports capable of allowing expansion phenomena, while blocking such supports in the event of dynamic stress.

PRIOR ART

The problem of protecting interconnected structures has existed for a long time. This problem has in particular concerned, and indeed still concerns, the seismic field, in which it is desired to preserve the civil engineering piece of work or building, or the structures that it comprises, from the violent accelerations inherent to earthquakes. In this context, it is desired to impart to said piece of work or to the structures which it comprises (such as pipes, etc.) a certain degree of freedom and movement inherent in particular to the phenomena of expansion.

In fact, numerous publications have addressed this problem known as seismic stops.

Traditionally, these seismic stops integrate hydraulic means with a damping function, of a cylinder-type. In addition to the substantial bulk that they generate, the ability to set the acceleration threshold beyond which such cylinders become blocking, that is to say prohibit the relative movement of the piece of work or structures of the piece of work with respect to its attachment point, is difficult to implement for applications other than seismic stops.

It has also been proposed the implementation of purely mechanical devices, such as, for example, in document EP O 171 405. This device operates by implementing the inertia resulting from the rotation of a movable element, following a relative movement of the two structures of which said device is secured, causing to the meshing of a ratchet toothing with a rotary part and a fixed part, generating the blocking of the rotation, and — therefore, relatedly, the blocking of the translation. During meshing, there is shock and wear on the teeth. Furthermore, the locking becomes effective only after a significant stroke of the elements carrying the respective teeth. In fact, in addition to the height of the teeth, it is advisable to add the functional clearance, leading to a distance that is too great to limit the effects of dynamic amplification. Finally, in the device described, there is only one screw capable of moving in both directions, and relatedly of locking, causing a torsion torgue on the screw which is difficultly compatible with the high forces, conseguently reducing the possible applications of such a device.

The aim of the present invention is to provide a device that is also purely mechanical, and — therefore excludes any hydraulic or pneumatic force, that is both simple to implement and capable of being configured to operate in traction, in compression, or even in traction/compression, and this over large ranges of forces, typically varying from a few kilos to several hundred tons.

DISCLOSURE OF THE INVENTION

The invention thus aims a device for mechanically blocking a linear movement between two structures, the device comprising: = afirst element secured to one of said structures; = a second element secured to or bearing against the other of said two structures.

According to the invention, said first and second elements cooperate linearly with each other by means of a double coaxial screw-nut pair: = a first screw-and-nut pair consisting of a so-called reversible screw and a nut cooperating without stress or almost without stress with said reversible screw; " a second screw-and-nut pair consisting of a so-called irreversible screw and a nut cooperating with said irreversible screw, the cooperation between these two elements having a determined clearance; one of the elements of the first pair being secured to one of the elements of the second pair, such that the rotation of one inherent to the relative linear movement of said first element with respect to the second element causes the rotation of the other.

This device also comprises at least one elastic means, capable of acting on one of the constituent elements of the mentioned above screw-and-nut pairs, so as to: " maintain the screw-and-nut clearance of said second pair when the stress is less than a threshold fixed by construction, said stress corresponding to a rotational speed of one of the elements of the pair; and = cause the blocking of the cooperation of elements of the second irreversible screw- and-nut pair beyond said stress threshold.

In other words, the invention consists in adjusting the clearance, which is certainly limited, but existing by construction between the so-called irreversible screw and the nut assigned thereto for, as a function of a specific stress inherent to the rotational speed of the assembly, rotation itself inherent to the relative linear movement between the two structures between which the device of the invention is mounted, allowing the rotation of the irreversible screw within the corresponding nut or, on the contrary, blocking it, the elastic means being intended to ensure the centering of said irreversible screw with respect to the assigned nut, and relatedly makes it possible to fix, as a function of its characteristics (the stiffness constant if it is a spring), the threshold beyond which the device becomes blocking.

In accordance with one embodiment of the invention, the reversible screw of the first pair is secured to the irreversible screw of the second pair, and the elastic means is secured to the two nuts of each of said pairs.

In accordance with another variation, the irreversible screw of the second pair is secured to the nut of the first pair (reversible screw-nut), and the elastic means acts on the reversible screw.

The invention also aims a stop for an oscillating mechanism, and a seismic stop implementing such a device. — BRIEF DESCRIPTION OF THE FIGURES

The manner in which the invention may be carried out and the resulting advantages appear more clearly from the following examples of carrying out, which are given by way of non-limited indication and with the support of the accompanying figures.

Figures1 and 2 schematically illustrate the operating principle of the device of the invention, respectively in free mode and in locked mode.

Figures 3 and 4 schematically show a particular application of the operating principle of the device of the invention, respectively in free mode and in locked mode.

Figure 5 is a schematic view of the upper end of a hoisting winch, Figure 6 being a detail — view, and Figure 7 illustrating the device of the invention applied to such a winch.

Figure 8 illustrates another application of the invention, in this case a seismic blocker, capable of operating in traction/compression mode.

Figure 9 illustrates another application of the invention, intended for a bridge crane.

Here again, Figure 10 illustrates the application of the device of the invention within the seismic field, but in horizontal recovery mode, implementing four devices illustrated in

Figure 9.

Figure 11 is a schematic representation of the upper part of Figure 7, but in which the so- called reversible screw is capable of moving in both directions.

DETAILED DESCRIPTION OF THE INVENTION

Figures 1 and 2 schematically represent the operating principle of the device of the invention. 5

This device is therefore intended to interact between two structures (1) and (2), and more specifically to regulate the relative movement of one with respect to the other. In this case, the movement that is to be regulated is a linear movement, illustrated by the right arrow (3).

By means of the device of the invention, this linear movement will be converted within the device into a rotational movement of parts of the constituent elements of said device.

In this block diagram, one of the elements, in this case constituted of a case (4), is secured to the structure (1), while the other element bears, for example by means of a pusher (5), — against the second structure (2). Alternatively, this second element could, for certain applications, be secured to said second structure (2).

This pusher (5), in the event of the structure (2) moving towards the structure (1), causes a screw (6), referred to as an irreversible screw, to rotate, the connection between said pusher and the screw (6) being free to rotate, but blocked in translation.

The irreversible screw (6) cooperates with an also so-called irreversible nut (7), secured to the case (4) which, as already stated, is itself secured to the structure (1). This irreversible screw (6) is moreover secured to a so-called reversible nut (8), such that the rotation of the irreversible screw (6) causes the reversible nut (8) to rotate. This reversible nut (8) is in turn capable of rotating about a so-called reversible screw (9). This notion of reversibility means the absence or virtual absence of mechanical stress during the cooperation of the reversible screw (9) with the reversible nut (8). — The reversible screw (9) is itself in elastic connection (10) with the case (4). This elastic connection typically results from the action of a spring, such that, moreover, it will have come back below.

This elastic connection makes it possible to ensure the centering of the irreversible screw (6) with respect to the irreversible nut (7), and therefore, relatedly, the free rotation of said screw (6) within the nut (7), or on the contrary, the blocking of the latter.

Thus, the calibration of the spring constituting the elastic connection (10) makes it possible to define the stress threshold beyond which there is blocking of the rotation of the irreversible screw (6) within the irreversible nut (7) (Figure 2), which blocking is inherent to a too intimate contact, and relatedly too intense friction, between the thread of the irreversible screw (6) on the tapping of the irreversible nut (7), de facto blocking any possibility of axial movement (3) between the two structures.

More precisely, the operation of such a device is based on the modification of the apparent length of said elastic connection. This variation in length is inherent to a modification of the stress state of said elastic length. Thus, during the relative movements — of the two structures according to the arrow (3), an element of the irreversible system, in this case the irreversible screw (6), is driven in rotation, and this rotation causes a resistant force, directly depending on the mass of said screw (6) in movement and on the acceleration imparted to the mechanism. The calibration of the spring, and for example the choice of its stiffness constant, is a function of the mass of the movable member, in — this case the screw (6), and of the maximum acceptable acceleration limit.

Figures 3 and 4 illustrate another block diagram of the invention. In this case, the reversible screw (9) and the irreversible screw (6) are collinear and secured to each other.

However, their screw pitch differs, since both, the screw pitch of the reversible screw (9) — is intended to cooperate with a nut typically with balls, therefore able to oppose as little resistance as possible to its free rotation, even though the irreversible screw (6) is a screw with a trapezoidal pitch for example, only the specific clearance existing between the irreversible screw (6) and the irreversible nut (7) not appearing in the figures. — In this schematic representation, the two nuts, respectively reversible (8) and irreversible (7), are linked in rotation, that is to say that the rotation of one causes the rotation of the other, provided that the prestressed spring (10), which has also been illustrated in the two diagrams, does not undergo too great a stress arising from the approximation of the distance D illustrated also in the diagrams. This distance D, and therefore the stiffness constant of the spring (10), is such that the irreversible screw/nut clearance (6, 7) is centered, and consequently, allows the free or almost free rotation of one with respect to the other.

Thus, in normal operation, that is to say for a thrust (left arrow in the figures) less than a threshold value, determined by the stiffness constant of the spring (10), the rotation of the reversible nut (8) generated by the linear movement of the reversible screw (9), simultaneously causes the rotation of the irreversible nut (7). The spring (10) induces to keep the distance D between the two nuts and this distance D, and therefore consequently — the calibration of the spring, is such that the screw/nut clearance of the irreversible or trapezoidal screw is centered, capable of allowing the nut (7) to rotate freely or almost freely on the screw (6). The two nuts therefore move in identical manner. In this normal operation, the force necessary to accelerate the irreversible nut (6) must be less than the prestress generated by the spring (10).

However (Figure 4), when the force on the reversible screw (9) is too great, and in particular greater than a threshold determined by the stiffness constant of the spring (10), this induces a rotational speed V of the reversible nut (8), and relatedly of the irreversible nut (7), such that the distance D', then less than D, is no longer kept by the spring (10), inducing the taking up of the clearance between the threads of the irreversible nut (7) on the irreversible screw (6), and relatedly the blocking of the rotation of one within the other, and therefore the immediate stopping of the relative movement between the two structures (not shown in Figures 3 and 4) to which the device is secured.

A particular application of the device of the invention to a hoisting winch, and more precisely to a stop of an oscillating mechanism, has been shown in relation to Figures 5, 6 and 7.

A hoisting winch conventionally comprises a balancing spreader beam (11), articulated — about an axis (12), and to both ends of which are secured two hoisting cables (13, 14).

One of the ends of each of these two cables is wound on hoisting drums (15, 16), the other end (17, 18) of said cables being connected to the two ends of the spreader beam on a device of the invention, after reeving, for example, on a hook to which a load (not shown) is fixed. In this case, the objective sought by the implementation of the device of the invention in such a winch is to block the oscillation of the spreader beam in the event of acceleration of said oscillation beyond a determined threshold, and resulting, for example, from the breakage of one of the cables, or from the untimely fall of the load.

In normal operation, the spreader beam must be able to oscillate in order to balance the tension in the hoisting cables (13, 14). In the event of one of said cables breaking, the balance is broken and the spreader beam tilts abruptly on the side of the cable which is still active until it comes into stop against the fixed frame (19) of the winch. This sudden stop generates very high dynamic forces, liable to jeopardize the integrity of the hoisting — chain, and relatedly the safety of the suspended load.

The objective sought by the implementation of the device of the invention at the spreader beam is to block the latter almost instantaneously in the event of acceleration of the oscillation of the latter, beyond a limit threshold determined by construction, and thus to — preserve the integrity of the hoisting chain.

More precisely, the first structure (1) of the device of the invention is therefore constituted by one of the ends of the spreader beam, and the second structure (2) bears on the frame (19) of the winch. Figure 7 illustrates more precisely the device of the invention — within this application.

In this Figure 7, reference (20) shows the pusher coming to bear on the frame (19) of the winch. This pusher (20) is advantageously protected by a bellows (21) against ambient dust, and is furthermore guided within a sheath (28) secured to a body (7), acting as an irreversible nut. The pusher (20) is secured to the irreversible screw (6) by a mechanical assembly (22) capable of ensuring a connection that is free in rotation but blocked in translation between these two elements. In other words, this connection prevents the pusher (20) to rotate, but allows the irreversible screw (6) to rotate.

The irreversible screw (6) secured to the pusher (20) is received within a tapped body, acting as an irreversible nut (7), and secured to the spreader beam (11), by means of an articulated connection (not shown). The thread of the body (7) is adapted to the external thread of the irreversible screw (6). More specifically, the irreversible screw (6) has a limited number of threads (23), in this case two, in order to allow the device of the invention to operate.

This irreversible screw (6) is secured to the reversible nut (8). As the body (7) is static because it is secured to the spreader beam (11), and furthermore because of the connection (22) between the pusher (20) and said irreversible screw (6), the movement of the pusher (20) causes the irreversible screw (6) to rotate because it co-operates with the body (7), and therefore relatedly causes the reversible nut (8) to rotate. Said reversible nut (8) rotates on a reversible screw (9), coaxial with the reversible nut, with the irreversible screw and with the irreversible nut. Furthermore, the reversible screw (9) is blocked in rotation, but not in translation, by a blocking spacer (24), integrated in a holding bell (25), secured to the body (7).

Finally, a calibration spring (10), bearing on said reversible screw (9), is also received in the holding bell (25), where it interacts with a calibration screw (26), intended to compress more or less said spring (10), and therefore to make it possible to set the stress threshold mentioned above.

The bell (25) thus holds the calibration screw (26) in translation and the locking spacer (24) in rotation.

Doing this, during the phases of speed of advance of the piston, and therefore of acceleration less than a threshold value, because of the choice of the respective reversible nut/reversible screw pairs on the one hand, and irreversible nut/irreversible screw pairs on — the other hand, the resistance opposite the rotational movement previously described is reduced.

However, if the acceleration of the piston, for example inherent in a breakage of one of the cables (13, 14), exceeds said threshold value, resulting in the acceleration of the rotation of the irreversible screw (6)/reversible nut (8) assembly, a resistance is generated between the threads (23) of said irreversible screw against the threads of the irreversible nut or body (7), which therefore blocks said rotation of the irreversible screw within the irreversible nut and, relatedly, the translational movement along the axis (27) of the device.

Thus, as long as the acceleration phases generate a force lower than the calibration force of the spring (10), the mechanism is totally reversible and does not oppose the translational movement along said axis (27).

However, when the force generated by the acceleration is higher than the calibration force of the spring (10), the axial position of the reversible screw (9) is modified and, relatedly, that of the irreversible screw (6), such that the clearance between the threads (23) of the irreversible screw (6) and those of the irreversible nut or body (7) is no longer maintained, generating friction appearing on the flanks of the threads and, relatedly, the blocking in rotation of said irreversible screw, and therefore of the assembly. In other words, the adjustment of the clearance existing between the irreversible screw (6) and the body (7) is refined by the action of the reversible screw (9) and the cooperation of the latter with the spring (10).

To this end, in the absence of stress higher than the threshold fixed by construction, the clearance existing between the irreversible screw (6) and the irreversible nut or body (7) is between 0.3 and 1 millimetre, that is to say that the thickness of the threads (23) of the irreversible screw (6) is typically 1 millimetre less than the width defined by the threads of the body (7) over the entire interaction distance between the respective threads.

Furthermore, this clearance can also result from the difference between the external diameter of the threads (23) at their maximum extension and the deepest diameter of the threads of the body (7). This difference may typically be close to 0.5 millimetre.

It is the reversible screw (9) and the action on the latter of the spring (10) which, as it were, ensures the sustentation of the irreversible screw (6) within the body (7) in the absence of stresses lower than the threshold fixed by construction, and therefore relatedly its possible rotation within said body.

However, as soon as the stress exceeds said threshold, there is firmer contact and friction between the irreversible screw (6) and the body (7), and relatedly, a blocking of the rotation of said screw within the body (7).

In the example described, the hoisting winch is typically a 140-tons winch, requiring a locking force close to 40 tons. The amplitude of the movement of the ends of the spreader beam is close to 30 millimetres. The constituent elements of the device of the invention are sized accordingly. Thus, the irreversible screw (6) is, for example, made of a light 3 alloy, such as, for example, aluminium AU4G or titanium, so as to limit its inertia, and relatedly, minimize the calibration force of the spring (10). Moreover, the angle defined by the respective threads, and the pitch can also be adjusted to allow the desired operation of the device. Advantageously, the angle of the threads of the irreversible screw (6) is smaller than the angle of the threads of the body (7). In that way, the compactness of the — entire device of the invention is optimized. The clearance carried out by construction between the irreversible screw (6) and the body (7) is also a parameter to be taken into consideration: typically, it is close to 0.5 millimetre.

Furthermore, the reversible nature of the screw (9) -nut (8) pair is optimized, for example by implementing a ball screw (20 mm pitch for example) - ball nut pair.

In the example described, this locking device operates for the compressive forces.

However, the device of the invention can also operate in traction, or even in both — directions of traction and compression. Thus, in relation to Figure 8, the device of the invention has been shown operating in both directions. In this case, the device is implemented in the context of a seismic stop. Thus, it is secured respectively to the foundations of a civil engineering piece of work and to the structure itself.

Figures 9 and 10 show the device of the invention at a bridge crane (30). The latter is capable of moving horizontally according to the double arrow of Figure 10. In order to preserve its integrity in the event of a seismic shock, the two lateral ends (31, 32) of the bridge crane incorporate four devices of the invention, one of the parts of which is capable of bearing on the load-bearing walls (33, 34) and of moving against the internal — surface of said walls. To this end, the pusher (20) is secured to a roller (35) mounted for free rotation on a support (36). Furthermore, in order to hold said roller (35) against the inner surface of the wall, gas cylinders (37) are secured respectively to the body (7) and to the support (36).

In that way, the assembly makes it possible to follow the flatness defects of the inner surface of the walls (31, 32) without affecting the operation of the bridge crane (30), which moves horizontally at low speed. However, in the event of acceleration due to a seismic shock, the device of the invention causes the bridge crane to be blocked and — relatedly makes it impossible for the bridge crane to move.

A detailed view of the upper part of Figure 7, in the particular case of the possible movement of the reversible screw (9) in both directions, is shown in relation to Figure 11.

To this end, one stress spring is no longer used, but two coaxial springs (40, 41) are used: e a lower spring (41) mounted between a lower stop (43) and a lower radial annular protrusion (44), arising from the screw (9); e an upper spring (40) mounted between an upper stop (42) and an upper radial annular protrusion (47), also arising from the screw (9).

These two springs are capable of acting on one of the constituent elements of the screw- nut pairs so as to generate two distinct stress thresholds, respectively in the two directions of the linear movement between the two structures (1, 2). — The respective lower (43) and upper (42) stops, secured to the holding bell (25), make it possible to adjust the calibration of the springs (40) and (41).

In that way, it becomes possible to define a different triggering threshold as a function of traction or compression, by adjusting the calibration and the stiffness constant of the two — springs (40) and (41) and on the stops (42) and (43).

Furthermore, it is also possible to envisage fine adjustment of the clearance defined by construction between the irreversible screw (6) and the body (7) (of Figure 7). To this end, the holding bell (25) is rotatably mounted with respect to the axis (27), its blocking according to the desired position being ensured by means of a nut (46). The cover (48), secured to the holding bell (25), is provided with a pin (45) directed downwards. This pin (45) is freely received in a bore (49) formed at the top end of the reversible screw (9). In other words, said reversible screw slides without stress, or almost without stress, along the pin.

By simple rotation of the holding bell, which causes the reversible screw (9) to rotate, it therefore becomes possible to adjust the clearance between the irreversible screw (6) and the body (7), by the action of the pin (45) on the reversible screw (9) on the one hand, and — by the screw-nut or interlocking connections existing between the two screw-nut pairs.

Once this fine adjustment has been made, the rotation of the holding bell is blocked by means of the nut (46).

Whatever the embodiment of the invention, as soon as the stress exerted on the device falls below the defined threshold, as described above, the operation of the latter automatically returns to reversible mode, because of the action of the spring which pushes the reversible screw back into its original position.

The whole advantage of the present invention is conceivable, which makes it possible in a — simple, efficient and compact manner to block the relative linear movement between two structures, and this within a very wide range of constraints.

Claims (11)

1. DEVICE FOR MECHANICAL LOCKING OF A LINEAR MOVEMENT BETWEEN TWO STRUCTURES FIELD OF THE INVENTION

   The invention relates to a device capable of allowing the relative movement of two structures with respect to one another under normal conditions of use or situation and, relatedly, of blocking this movement when said so-called normal conditions are not met anymore.

   This device is intended in particular to protect all or part of the constituent — elements of said structures.

   In particular, it finds application: " within oscillating mechanisms of the balance type, to allow the movement of said balance to be blocked in the event of a rapid imbalance, such as in the field of hoisting winches for example; = within seismic stops; = within stops for air/hydraulic valves/doors, in order to block this system in the event of sudden stresses inherent to the windstorms, explosions, etc.; = within the protection of the mechanisms of doors, traps or hatches, in order to protect the opening mechanisms in the event of an explosion or exceptional stress; " within the stabilisation of equipment subject to strong accelerations in the field of aeronautics, maritime and land vehicles; = within pipework supports capable of allowing expansion phenomena, while blocking such supports in the event of dynamic stress.

   PRIOR ART The problem of protecting interconnected structures has existed for a long time.

   This problem has in particular concerned, and indeed still concerns, the seismic field, in which it is desired to preserve the civil engineering piece of work or building, or the structures that it comprises, from the violent accelerations inherent to earthquakes.

   In this context, it is desired to impart to said piece of work or to the structures which it comprises (such as pipes, etc.) a certain degree of freedom and movement inherent in particular to the phenomena of expansion.

   In fact, numerous publications have addressed this problem known as seismic stops.

   Traditionally, these seismic stops integrate hydraulic means with a damping function, of a cylinder-type.

   In addition to the substantial bulk that they generate, the ability to set the acceleration threshold beyond which such cylinders become blocking, that is to say prohibit the relative movement of the piece of work or structures of the piece of work with respect to its attachment point, is difficult to implement for applications other than seismic stops.

   It has also been proposed the implementation of purely mechanical devices, such as, for example, in document EP O 171 405. This device operates by implementing the inertia resulting from the rotation of a movable element, following a relative movement of the two structures of which said device is secured, causing to the meshing of a ratchet toothing with a rotary part and a fixed part, generating the blocking of the rotation, and

   — therefore, relatedly, the blocking of the translation.

   During meshing, there is shock and wear on the teeth.

   Furthermore, the locking becomes effective only after a significant stroke of the elements carrying the respective teeth.

   In fact, in addition to the height of the teeth, it is advisable to add the functional clearance, leading to a distance that is too great to limit the effects of dynamic amplification.

   Finally, in the device described, there is only one screw capable of moving in both directions, and relatedly of locking, causing a torsion torgue on the screw which is difficultly compatible with the high forces, conseguently reducing the possible applications of such a device.

   The aim of the present invention is to provide a device that is also purely mechanical, and

   — therefore excludes any hydraulic or pneumatic force, that is both simple to implement and capable of being configured to operate in traction, in compression, or even in traction/compression, and this over large ranges of forces, typically varying from a few kilos to several hundred tons.

   DISCLOSURE OF THE INVENTION

   The invention thus aims a device for mechanically blocking a linear movement between two structures, the device comprising:

   = afirst element secured to one of said structures;

   = a second element secured to or bearing against the other of said two structures.

   According to the invention, said first and second elements cooperate linearly with each other by means of a double coaxial screw-nut pair:

   = a first screw-and-nut pair consisting of a so-called reversible screw and a nut cooperating without stress or almost without stress with said reversible screw;

   " a second screw-and-nut pair consisting of a so-called irreversible screw and a nut cooperating with said irreversible screw, the cooperation between these two elements having a determined clearance;

   one of the elements of the first pair being secured to one of the elements of the second pair, such that the rotation of one inherent to the relative linear movement of said first element with respect to the second element causes the rotation of the other.

   This device also comprises at least one elastic means, capable of acting on one of the constituent elements of the mentioned above screw-and-nut pairs, so as to:

   " maintain the screw-and-nut clearance of said second pair when the stress is less than a threshold fixed by construction, said stress corresponding to a rotational speed of one of the elements of the pair; and

   = cause the blocking of the cooperation of elements of the second irreversible screw-

   and-nut pair beyond said stress threshold.

   In other words, the invention consists in adjusting the clearance, which is certainly limited, but existing by construction between the so-called irreversible screw and the nut assigned thereto for, as a function of a specific stress inherent to the rotational speed of the assembly, rotation itself inherent to the relative linear movement between the two structures between which the device of the invention is mounted, allowing the rotation of the irreversible screw within the corresponding nut or, on the contrary, blocking it, the elastic means being intended to ensure the centering of said irreversible screw with respect to the assigned nut, and relatedly makes it possible to fix, as a function of its characteristics (the stiffness constant if it is a spring), the threshold beyond which the device becomes blocking.

   In accordance with one embodiment of the invention, the reversible screw of the first pair is secured to the irreversible screw of the second pair, and the elastic means is secured to the two nuts of each of said pairs.

   In accordance with another variation, the irreversible screw of the second pair is secured to the nut of the first pair (reversible screw-nut), and the elastic means acts on the reversible screw.

   The invention also aims a stop for an oscillating mechanism, and a seismic stop implementing such a device. — BRIEF DESCRIPTION OF THE FIGURES The manner in which the invention may be carried out and the resulting advantages appear more clearly from the following examples of carrying out, which are given by way of non-limited indication and with the support of the accompanying figures.

   Figures1 and 2 schematically illustrate the operating principle of the device of the invention, respectively in free mode and in locked mode.

   Figures 3 and 4 schematically show a particular application of the operating principle of the device of the invention, respectively in free mode and in locked mode.

   Figure 5 is a schematic view of the upper end of a hoisting winch, Figure 6 being a detail — view, and Figure 7 illustrating the device of the invention applied to such a winch.

   Figure 8 illustrates another application of the invention, in this case a seismic blocker, capable of operating in traction/compression mode.

   Figure 9 illustrates another application of the invention, intended for a bridge crane.

   Here again, Figure 10 illustrates the application of the device of the invention within the seismic field, but in horizontal recovery mode, implementing four devices illustrated in Figure 9. Figure 11 is a schematic representation of the upper part of Figure 7, but in which the so- called reversible screw is capable of moving in both directions.

   DETAILED DESCRIPTION OF THE INVENTION Figures 1 and 2 schematically represent the operating principle of the device of the invention. 5 This device is therefore intended to interact between two structures (1) and (2), and more specifically to regulate the relative movement of one with respect to the other.

   In this case, the movement that is to be regulated is a linear movement, illustrated by the right arrow (3).

   By means of the device of the invention, this linear movement will be converted within the device into a rotational movement of parts of the constituent elements of said device.

   In this block diagram, one of the elements, in this case constituted of a case (4), is secured to the structure (1), while the other element bears, for example by means of a pusher (5), — against the second structure (2). Alternatively, this second element could, for certain applications, be secured to said second structure (2). This pusher (5), in the event of the structure (2) moving towards the structure (1), causes a screw (6), referred to as an irreversible screw, to rotate, the connection between said pusher and the screw (6) being free to rotate, but blocked in translation.

   The irreversible screw (6) cooperates with an also so-called irreversible nut (7), secured to the case (4) which, as already stated, is itself secured to the structure (1). This irreversible screw (6) is moreover secured to a so-called reversible nut (8), such that the rotation of the irreversible screw (6) causes the reversible nut (8) to rotate.

   This reversible nut (8) is in turn capable of rotating about a so-called reversible screw (9). This notion of reversibility means the absence or virtual absence of mechanical stress during the cooperation of the reversible screw (9) with the reversible nut (8). — The reversible screw (9) is itself in elastic connection (10) with the case (4). This elastic connection typically results from the action of a spring, such that, moreover, it will have come back below.

   This elastic connection makes it possible to ensure the centering of the irreversible screw (6) with respect to the irreversible nut (7), and therefore, relatedly, the free rotation of said screw (6) within the nut (7), or on the contrary, the blocking of the latter.

   Thus, the calibration of the spring constituting the elastic connection (10) makes it possible to define the stress threshold beyond which there is blocking of the rotation of the irreversible screw (6) within the irreversible nut (7) (Figure 2), which blocking is inherent to a too intimate contact, and relatedly too intense friction, between the thread of the irreversible screw (6) on the tapping of the irreversible nut (7), de facto blocking any possibility of axial movement (3) between the two structures.

   More precisely, the operation of such a device is based on the modification of the apparent length of said elastic connection.

   This variation in length is inherent to a modification of the stress state of said elastic length.

   Thus, during the relative movements

   — of the two structures according to the arrow (3), an element of the irreversible system, in this case the irreversible screw (6), is driven in rotation, and this rotation causes a resistant force, directly depending on the mass of said screw (6) in movement and on the acceleration imparted to the mechanism.

   The calibration of the spring, and for example the choice of its stiffness constant, is a function of the mass of the movable member, in

   — this case the screw (6), and of the maximum acceptable acceleration limit.

   Figures 3 and 4 illustrate another block diagram of the invention.

   In this case, the reversible screw (9) and the irreversible screw (6) are collinear and secured to each other.

   However, their screw pitch differs, since both, the screw pitch of the reversible screw (9)

   — is intended to cooperate with a nut typically with balls, therefore able to oppose as little resistance as possible to its free rotation, even though the irreversible screw (6) is a screw with a trapezoidal pitch for example, only the specific clearance existing between the irreversible screw (6) and the irreversible nut (7) not appearing in the figures.

   — In this schematic representation, the two nuts, respectively reversible (8) and irreversible (7), are linked in rotation, that is to say that the rotation of one causes the rotation of the other, provided that the prestressed spring (10), which has also been illustrated in the two diagrams, does not undergo too great a stress arising from the approximation of the distance D illustrated also in the diagrams.

   This distance D, and therefore the stiffness constant of the spring (10), is such that the irreversible screw/nut clearance (6, 7) is centered, and consequently, allows the free or almost free rotation of one with respect to the other.

   Thus, in normal operation, that is to say for a thrust (left arrow in the figures) less than a threshold value, determined by the stiffness constant of the spring (10), the rotation of the reversible nut (8) generated by the linear movement of the reversible screw (9), simultaneously causes the rotation of the irreversible nut (7). The spring (10) induces to keep the distance D between the two nuts and this distance D, and therefore consequently

   — the calibration of the spring, is such that the screw/nut clearance of the irreversible or trapezoidal screw is centered, capable of allowing the nut (7) to rotate freely or almost freely on the screw (6). The two nuts therefore move in identical manner.

   In this normal operation, the force necessary to accelerate the irreversible nut (6) must be less than the prestress generated by the spring (10).

   However (Figure 4), when the force on the reversible screw (9) is too great, and in particular greater than a threshold determined by the stiffness constant of the spring (10), this induces a rotational speed V of the reversible nut (8), and relatedly of the irreversible nut (7), such that the distance D', then less than D, is no longer kept by the spring (10),

   inducing the taking up of the clearance between the threads of the irreversible nut (7) on the irreversible screw (6), and relatedly the blocking of the rotation of one within the other, and therefore the immediate stopping of the relative movement between the two structures (not shown in Figures 3 and 4) to which the device is secured.

   A particular application of the device of the invention to a hoisting winch, and more precisely to a stop of an oscillating mechanism, has been shown in relation to Figures 5, 6 and 7.

   A hoisting winch conventionally comprises a balancing spreader beam (11), articulated

   — about an axis (12), and to both ends of which are secured two hoisting cables (13, 14). One of the ends of each of these two cables is wound on hoisting drums (15, 16), the other end (17, 18) of said cables being connected to the two ends of the spreader beam on a device of the invention, after reeving, for example, on a hook to which a load (not shown) is fixed.

   In this case, the objective sought by the implementation of the device of the invention in such a winch is to block the oscillation of the spreader beam in the event of acceleration of said oscillation beyond a determined threshold, and resulting, for example, from the breakage of one of the cables, or from the untimely fall of the load.

   In normal operation, the spreader beam must be able to oscillate in order to balance the tension in the hoisting cables (13, 14). In the event of one of said cables breaking, the balance is broken and the spreader beam tilts abruptly on the side of the cable which is still active until it comes into stop against the fixed frame (19) of the winch.

   This sudden stop generates very high dynamic forces, liable to jeopardize the integrity of the hoisting

   — chain, and relatedly the safety of the suspended load.

   The objective sought by the implementation of the device of the invention at the spreader beam is to block the latter almost instantaneously in the event of acceleration of the oscillation of the latter, beyond a limit threshold determined by construction, and thus to

   — preserve the integrity of the hoisting chain.

   More precisely, the first structure (1) of the device of the invention is therefore constituted by one of the ends of the spreader beam, and the second structure (2) bears on the frame (19) of the winch.

   Figure 7 illustrates more precisely the device of the invention

   — within this application.

   In this Figure 7, reference (20) shows the pusher coming to bear on the frame (19) of the winch.

   This pusher (20) is advantageously protected by a bellows (21) against ambient dust, and is furthermore guided within a sheath (28) secured to a body (7), acting as an irreversible nut.

   The pusher (20) is secured to the irreversible screw (6) by a mechanical assembly (22) capable of ensuring a connection that is free in rotation but blocked in translation between these two elements.

   In other words, this connection prevents the pusher (20) to rotate, but allows the irreversible screw (6) to rotate.

   The irreversible screw (6) secured to the pusher (20) is received within a tapped body, acting as an irreversible nut (7), and secured to the spreader beam (11), by means of an articulated connection (not shown). The thread of the body (7) is adapted to the external thread of the irreversible screw (6). More specifically, the irreversible screw (6) has a limited number of threads (23), in this case two, in order to allow the device of the invention to operate.

   This irreversible screw (6) is secured to the reversible nut (8). As the body (7) is static because it is secured to the spreader beam (11), and furthermore because of the connection (22) between the pusher (20) and said irreversible screw (6), the movement of the pusher (20) causes the irreversible screw (6) to rotate because it co-operates with the body (7), and therefore relatedly causes the reversible nut (8) to rotate.

   Said reversible nut (8) rotates on a reversible screw (9), coaxial with the reversible nut, with the irreversible screw and with the irreversible nut.

   Furthermore, the reversible screw (9) is blocked in rotation, but not in translation, by a blocking spacer (24), integrated in a holding bell (25), secured to the body (7). Finally, a calibration spring (10), bearing on said reversible screw (9), is also received in the holding bell (25), where it interacts with a calibration screw (26), intended to compress more or less said spring (10), and therefore to make it possible to set the stress threshold mentioned above.

   The bell (25) thus holds the calibration screw (26) in translation and the locking spacer (24) in rotation.

   Doing this, during the phases of speed of advance of the piston, and therefore of acceleration less than a threshold value, because of the choice of the respective reversible nut/reversible screw pairs on the one hand, and irreversible nut/irreversible screw pairs on — the other hand, the resistance opposite the rotational movement previously described is reduced.

   However, if the acceleration of the piston, for example inherent in a breakage of one of the cables (13, 14), exceeds said threshold value, resulting in the acceleration of the rotation of the irreversible screw (6)/reversible nut (8) assembly, a resistance is generated between the threads (23) of said irreversible screw against the threads of the irreversible nut or body (7), which therefore blocks said rotation of the irreversible screw within the irreversible nut and, relatedly, the translational movement along the axis (27) of the device.

   Thus, as long as the acceleration phases generate a force lower than the calibration force of the spring (10), the mechanism is totally reversible and does not oppose the translational movement along said axis (27).

   However, when the force generated by the acceleration is higher than the calibration force of the spring (10), the axial position of the reversible screw (9) is modified and, relatedly, that of the irreversible screw (6), such that the clearance between the threads (23) of the irreversible screw (6) and those of the irreversible nut or body (7) is no longer maintained, generating friction appearing on the flanks of the threads and, relatedly, the blocking in rotation of said irreversible screw, and therefore of the assembly.

   In other words, the adjustment of the clearance existing between the irreversible screw (6) and the body (7) is refined by the action of the reversible screw (9) and the cooperation of the latter with the spring (10).

   To this end, in the absence of stress higher than the threshold fixed by construction, the clearance existing between the irreversible screw (6) and the irreversible nut or body (7) is between 0.3 and 1 millimetre, that is to say that the thickness of the threads (23) of the irreversible screw (6) is typically 1 millimetre less than the width defined by the threads of the body (7) over the entire interaction distance between the respective threads.

   Furthermore, this clearance can also result from the difference between the external diameter of the threads (23) at their maximum extension and the deepest diameter of the threads of the body (7). This difference may typically be close to 0.5 millimetre.

   It is the reversible screw (9) and the action on the latter of the spring (10) which, as it were, ensures the sustentation of the irreversible screw (6) within the body (7) in the absence of stresses lower than the threshold fixed by construction, and therefore relatedly its possible rotation within said body.

   However, as soon as the stress exceeds said threshold, there is firmer contact and friction between the irreversible screw (6) and the body (7), and relatedly, a blocking of the rotation of said screw within the body (7).

   In the example described, the hoisting winch is typically a 140-tons winch, requiring a locking force close to 40 tons.

   The amplitude of the movement of the ends of the spreader beam is close to 30 millimetres.

   The constituent elements of the device of the invention are sized accordingly.

   Thus, the irreversible screw (6) is, for example, made of a light 3 alloy, such as, for example, aluminium AU4G or titanium, so as to limit its inertia, and relatedly, minimize the calibration force of the spring (10). Moreover, the angle defined by the respective threads, and the pitch can also be adjusted to allow the desired operation of the device.

   Advantageously, the angle of the threads of the irreversible screw (6) is smaller than the angle of the threads of the body (7). In that way, the compactness of the

   — entire device of the invention is optimized.

   The clearance carried out by construction between the irreversible screw (6) and the body (7) is also a parameter to be taken into consideration: typically, it is close to 0.5 millimetre.

   Furthermore, the reversible nature of the screw (9) -nut (8) pair is optimized, for example by implementing a ball screw (20 mm pitch for example) - ball nut pair.

   In the example described, this locking device operates for the compressive forces.

   However, the device of the invention can also operate in traction, or even in both

   — directions of traction and compression.

   Thus, in relation to Figure 8, the device of the invention has been shown operating in both directions.

   In this case, the device is implemented in the context of a seismic stop.

   Thus, it is secured respectively to the foundations of a civil engineering piece of work and to the structure itself.

   Figures 9 and 10 show the device of the invention at a bridge crane (30). The latter is capable of moving horizontally according to the double arrow of Figure 10. In order to preserve its integrity in the event of a seismic shock, the two lateral ends (31, 32) of the bridge crane incorporate four devices of the invention, one of the parts of which is capable of bearing on the load-bearing walls (33, 34) and of moving against the internal

   — surface of said walls.

   To this end, the pusher (20) is secured to a roller (35) mounted for free rotation on a support (36). Furthermore, in order to hold said roller (35) against the inner surface of the wall, gas cylinders (37) are secured respectively to the body (7) and to the support (36).

   In that way, the assembly makes it possible to follow the flatness defects of the inner surface of the walls (31, 32) without affecting the operation of the bridge crane (30), which moves horizontally at low speed.

   However, in the event of acceleration due to a seismic shock, the device of the invention causes the bridge crane to be blocked and — relatedly makes it impossible for the bridge crane to move.

   A detailed view of the upper part of Figure 7, in the particular case of the possible movement of the reversible screw (9) in both directions, is shown in relation to Figure 11. To this end, one stress spring is no longer used, but two coaxial springs (40, 41) are used: e a lower spring (41) mounted between a lower stop (43) and a lower radial annular protrusion (44), arising from the screw (9); e an upper spring (40) mounted between an upper stop (42) and an upper radial annular protrusion (47), also arising from the screw (9).

   These two springs are capable of acting on one of the constituent elements of the screw- nut pairs so as to generate two distinct stress thresholds, respectively in the two directions of the linear movement between the two structures (1, 2). — The respective lower (43) and upper (42) stops, secured to the holding bell (25), make it possible to adjust the calibration of the springs (40) and (41). In that way, it becomes possible to define a different triggering threshold as a function of traction or compression, by adjusting the calibration and the stiffness constant of the two — springs (40) and (41) and on the stops (42) and (43). Furthermore, it is also possible to envisage fine adjustment of the clearance defined by construction between the irreversible screw (6) and the body (7) (of Figure 7). To this end, the holding bell (25) is rotatably mounted with respect to the axis (27), its blocking according to the desired position being ensured by means of a nut (46). The cover (48), secured to the holding bell (25), is provided with a pin (45) directed downwards.

   This pin (45) is freely received in a bore (49) formed at the top end of the reversible screw (9). In other words, said reversible screw slides without stress, or almost without stress, along the pin.

   By simple rotation of the holding bell, which causes the reversible screw (9) to rotate, it therefore becomes possible to adjust the clearance between the irreversible screw (6) and the body (7), by the action of the pin (45) on the reversible screw (9) on the one hand, and

   — by the screw-nut or interlocking connections existing between the two screw-nut pairs.

   Once this fine adjustment has been made, the rotation of the holding bell is blocked by means of the nut (46).

   Whatever the embodiment of the invention, as soon as the stress exerted on the device falls below the defined threshold, as described above, the operation of the latter automatically returns to reversible mode, because of the action of the spring which pushes the reversible screw back into its original position.

   The whole advantage of the present invention is conceivable, which makes it possible in a — simple, efficient and compact manner to block the relative linear movement between two structures, and this within a very wide range of constraints.